This invention relates to a pressure plug apparatus having a safety retainer unit to prevent dangerous propelling of the plug unit in the event of failure of the plug unit and particularly a pressure test plug unit.
Various piping and vessel systems require pressure testing in the initial fabrication as well as during the operative life of the product. Internal combustion engines require a radiator for air cooling of the liquid solution of the engine cooling system. The radiators present a typical pressure vessel which is periodically pressure tested. The present invention has been particularly applied to testing of large radiators of internal combustion engines connected to drive electrical generators, and will be described in connection therewith. However, the invention can be equally applied to any pressurized system through which carries a high pressure medium and which includes a projecting tubular member. In pressure testing systems, there is always a danger that the test plug unit may be blown from the tubular member, and a safety connector unit often is required.
Typical prior art testing assemblies including a safety connector between the releasable plug and the product are shown in U.S. Pat. Nos. 508,609 issued Nov. 14, 1893; 1,226,023 issued May 15, 1917; 1,557,966 issued Oct. 20, 1925; and 2,238,257 issued Apr. 15, 1941. The very early '609 patent discloses a pipe member, one end of which is releasably sealed by an expansion plug, in which a threaded bolt unit is adapted to apply a collapsing force to the rubber member; expanding the rubber member into sealing engagement with the pipe. The pipe end has an outer fixed retainer with outwardly projecting ear members. A cable is wrapped about the ears and the exterior of the clamping bolt unit to positively hold the expansion plug to the pipe. Test pressure is applied through the threaded coupling pipe to pressurize the pipe with the rope band positively preventing blowing of the plug from the pipe under test conditions.
U.S. Pat. Nos. '966 and '257 show somewhat similar systems, each having a sealing plug member with means for expanding of the plug member within the pipe. A yoke member is telescoped over the plug member and pipe end, with interengaging wall structures which prevent the plug member from moving outwardly of the yoke. Generally, a plurality of arm members project from the yoke outwardly and axially over the pipe end, which has suitable enlargements. Locking of the safety device to the pipe and through the yoke to the plug member prevents projection of the plug member under high pressure conditions.
U.S. Pat. No. 986,297 discloses a similar expanding plug unit with a safety mechanism including a yoke secured to the expanding plug structure and arms which project down over the pipe end, with set screws threaded through the extended arms into locking engagement with the pipe end.
U.S. Pat. No. 1,226,023 discloses a system in which an expanding plug is located set inwardly of the pipe end. A separate locking mechanism is secured overlapping the outer end of the projecting pipe, with an inner toothed arm and an outer screw member for rigidly clamping of the assembly into engagement with the pipe. The inner end of the tooth member may indirectly engage a portion of the plug to releasably lock it in place. Alternatively, where the pipe has an enlarged diameter end, separate arm members, pivotally secured to the safety unit, are pivoted inwardly into engagement with the structure of the test plug.
All such safety devices generally use a plurality of different parts, often requiring an enlargement on the pipe end or merely relying on the pressure of set screws to hold the safety device in place.
Also, the prior art does not generally lock the safety unit to the plug unit. Although expanding stoppers for marine application, generally known as bailer plugs, are often provided with an interconnection such as a chain and a screw member, for attaching of the unit to the boat transom adjacent a bailer opening. The expanding plug is located within the bailer opening, and removed for releasing water from within the boat. The chain structure allows the user to temporarily open the bailer opening while maintaining of the plug attached to the boat for convenient replacement. Such a system is not particularly adapted to the pressure testing of vessels and fixed pipe members, where the test plug is only to be temporarily applied to the unit and then removed for use elsewhere.
Although various test plug systems are available and have been suggested over a period of approximately 80 years, the prior art has certain disadvantages from the standpoint of complexity, with initial cost as well as relatively time consuming application requiring special pipe ends and the like. The inventor recognized there is a need for a test assembly in which a safety latch unit which can be readily coupled to a tubular test plug unit and which test assembly can be readily applied to a tubular structure of the pressure vessel without requiring a special end construction, or relying on any great skill with respect to the proper attachment of the assembly in place, such as may be required with the prior art systems, including set screws, cables and the like.